Plastics moulding presses

ABSTRACT

A moulding press has a series of hollow guide bolts, each connected at one end to a plate of the press and having a head defining the maximum distance of another plate that slides on the bolt. A pin is contained slidably in the bolt and has transverse spikes protruding through longitudinal slots in the wall of the bolt. The spikes engage certain plates of the press to define their maximum movements.

United States Patent Veneria [54] PLASTICS MOULDING PRESSES [75]Inventor: Giovanni Bessolo Veneria, lvrea, Italy [73] Assignee: Ing. C.Olivetti 8: C;S.p.A., lvrea,

Italy Filed: Sept. 3, 1971 Appl. N0.: 177,607

[30] Foreign Application Priority Data Sept. 18, 1970 Italy ..70145 A/7O52 us. Cl. ..249/67, 425/242, 425/443, 425/DIG. 51 Int. Cl. ..B28b 7 10Field of Search ..249/67, 68, 161; 425/242, 443, 425/444, DIG. 51

Primary ExaminerH. A. Kilby, Jr. Attorney-Harold J. Birch et al.

57 ABSTRACT A moulding press has a series of hollow guide bolts, eachconnected at one end to a plate of the press and having a head definingthe maximum distance of another plate that slides on the bolt. A pin ,iscontained slidably in the bolt and has transverse spikes protrudingthrough longitudinal slots in the wall of the bolt. The spikes engagecertain plates of the press to define their maximum movements.

4 Claims, 9 Drawing Figures PATENTEDAPR 3 I973 3. 724.802

SHEET u 0F 8 FIG. 4

PATENTEBAPRE 192s SHEET 5 BF 8 PLASTICS MOULDING PRESSES This inventionrelates to moulding presses of the type in which articles are formedfrom plastics material. The article is usually-made byinjection-moulding, and is formed together with a deadhead (otherwiseknown as a sprue or moulding flash), the two being separated aftercooling.

' In such presses, injection takes place through a nozzle mounted in afixed plate, the material being injected into a cavity defined betweendies held by other plates. To permit opening and closing of the pressand ejection of the article and deadhead, some of the plates areslidable relatively to the fixed plate on guide rods passinglongitudinally through the press. Generally there are four guide rods,located one at each corner of the plates, which are rectangular.

To limit the extent of movement of one plate relatively to another, itis customary to provide a number of guide bolts. Such bolts are usuallyfixed at one end to a first plate and pass through an aperture in one ormore other plates that are thus slidable on the bolt relatively to thefirst plate. An enlarged head is provided on the free end of the bolt,and abutment of a plate against the head defines the maximum movement ofthat plate relatively to the plate to which the other end of the bolt isfixed.

In presses having three movable plates (or three sets of plates, theplates of each set being joined rigidly to each other) in addition tothe fixed plate and to certain ancillary plates on which are mountedejector pins, it is not uncommon to have as many as eight such guidebolts located at different points in the press. This has thedisadvantage of extreme complexity. Moreover, sirice'the guide bolts andthe guide rods all occupy space around the dies, it is difficult to gainaccess to the die cavity when the press is open for such purposes as tobrush it in order to ensure that no particles of plastics materialremain attached to it. It is customary to provide for such brushing ineach operating cycle as a security measure, but the automation of thebrushing operation is sometimes made difficult by the multiplicity ofbolts.

An object of the invention is to provide a moulding press in which thisdisadvantage is substantially reduced by reducing the space occupied bythe guide bolts.

The invention provides a moulding press having a plurality of plates andmeans to guide the plates for movement relatively to each other, suchguide means including a guide bolt extending between at least twoplates, with the improvement that the bolt is hollow and contains asliding pin, the pin having at least two transverse elements protrudingthrough slots in the bolt, each element being engageable with a plate tolimit the movement of that plate relatively to another plate.

In a preferred form, there are a first plate to which one end of thebolt is connected, the bolt having a head on its free end, and a secondplate and a third plate that are slidable on the bolt, the third platebeing adapted to engage the head of the bolt to define the maximum gapbetween the first and the third plates, the pin having a firstprotruding element in the form of a spike that is fixed to the secondplate and a second spike that is unconnected to any plate but is adaptedto engage a seat in the third plate when the third plate approaches thehead of the bolt on opening of the press, thereby to cause the pin andthe second plate to be moved together with the third plate away from thefirst plate.

In practice the first plate is usually a fixed plate of the press.

An embodiment of the invention is described below with reference to theaccompanying drawings, in which:

FIG. 1 is a simplified longitudinal sectioned view through the plates ofa closed injection-moulding press, taken along the line I-I of FIG. 2;

FIG. 2 is a view along the line II--II of FIG. 1, partly broken away toshow interior details; FIGS. 3 to 7 are views on a reduced scale of thepress of FIG. I, seen at intermediate phases' in the operating cycle ofthe press;

FIG. 8 is a fragmentary perspective view of a part of the press seen inFIGS. 1 to 7, arranged for purposes of illustration and not representingany phase in the operating cycle;

FIG. 9 is a perspective view from below of a hook used in the press ofthe preceding figures.

In FIG. 1, an injection-moulding press has the customary fixed backingplate 10 to which is attached a nozzle 12 for the injection of hotplastics material. The nozzle has a conventional undercut tip 14.Rigidly attached to the backing plate 10 is a fixed plate 16. Attachedto the plate 16 at diametrically opposite points (FIG. 2) are two hollowguide bolts 18, each held against rotation in the press by aspike 20(FIG. 1) which is rigid with the bolt 18 and seats in a groove 22 (FIG.8) in the plate 16, and further held against movement by a grub screw 21(FIGS. 1 and 8). The bolt 18 has an enlarged head 24 at its free end.The bolt 18 is otherwise of circular section, buthas a longitudinal flator land 26 (FIG. 8) on its radially outer surface, the flat 26 endingnear the head 24 in a sloping cam 28. At its other end, the flat 26extends to a position nearby the plate 16. Slidable within the cavity ofthe bolt 18 is a pin 30 (FIG. 1).

Flush with the plate 16 in FIG. 1 is a sliding plate' 32 which has acentral aperture accomodating the nozzle 12 and, for each bolt 18, arecess in which is seated a protruding element in the form of a spike36. The spike 36 is solid with the pin 30 near one of its ends andextends transversely of it, projecting through twolongitudinal slots 38in the bolt 18. Aninsert plate 40 is fixed to the plate 32 to ensurethat the spike 36 and hence the pin 30 are rigidly secured to the plate32. The slots 38 allow sliding movement of the plate 32 on the bolts 18between a position in which the plate 32 is flush with the plate 16(FIG. 1) and a position in which the two plates are spaced apart by adistance L (FIG. 4).

Flush with the plate 32 in FIG. 1 is a further plate 42 in which is helda female member 44 of the die of the press. Secured in a suitably shapedcavity in the plate 42 at each bolt 18 is a striking plate having twoteeth 52 (FIG. 8) whose purpose will be explained later.

Also formed in the plate 42 near each bolt 18 is a rebate or step 54 onwhich a spike 56 fixed in the pin 30 mayv abut, the spike 56 passingthrough longitudinal slots 58 in the bolt 18. The spike 56 is movableout of the rebate 54 when the plate 42 moves inwardly (i.e'. towards theplate 16) on closure of the press, as will emerge more fully below. Thespike 56 is held rigidly in position near the outer end of the pin 30 bymeans of a grub screw 59 (FIG. 1). The plate 41 also have a rebate 64(FIG. 1) on which the head 24 of thebolt 18 can abut in certainpositions of the press.

Outwardly of the plate 42 in FIG. 1 and flush with it is a furthermovable plate 60 in which is fixed the male 7 die member 62. A plate 61fixed to the plate 61 by bolts 79 holds the die member 62 firmly inplace. The plate 60 is bored to allow the passage through itself of apin 46 whose end abuts in FIG. 1 on the plate 42. A longitudinal cavity66 is provided in the plates 60,61 to allow the passage of each bolt 18.The cavity 66 is also partly occupied by a hook 68 hinged to the body ofthe plate 60 by means of a pair of pivots 70 (FIG. 8) extending intoflanges 71 (FIG. 9) on the undersurface of the hook 68 The pivots 70allow oscillating movement of the hook 68 about a transverse axis. Thepivots 70 are held in place by plates 72 (FIG. 8) screwed to the body ofthe plate 60. The hook 68 has a latch 74 (FIG. 9) which can engagetheteeth 52 fixed on the plate 42. The hook 68 is biased into a positionpromoting such engagement by springs .76 that react on the plate 60. Theend of the hook 68 carrying the latch 74 has an inclined face 78.

The plates 60,61 are rigidly connected by the bolts 79 (only one ofwhich is seen) to an annular body 80 acting as a spacer and having alongitudinal groove 82 that is a continuation of the groove 66 intheplates 60,61. The body 80 is in turn rigidly connected by the bolts79 to a plate 84 which has a bore 86 for each bolt 18, and a centralbore 88 into which extends a fluid cylinder 89 having a piston shaft 91.

Accommodated in the cavity of the body 80 is an ancillary plate 90 towhich the piston shaft 91 is connected and to which are rigidly fixed anumber of ejec tor pins.92,'the pins-92 being adapted to extend into themale die 62 for ejection of a formed article. The plate 90 is thusattached to and guided by the piston shaft 91 for longitudinal movementrelatively to the plates 60,61 and 84. The plate 90 also receives anenlarged head 94 on the pin 46, together with a spring 96 which biasesthe pin 46 inwardly towards the plate 42 and takes up small inaccuraciesin the dimensions of the components.

As seen in FIG. 2, the plates, 16,32,42,60,61,84 are pierced at their.corners and receive hollow guide bushes 98 which keep these platescorrectly aligned during their relative movements longitudinally in thepress by co-operating with solid guide rods 99 fixed to one of theplates. For simplicitys sake the rods 99 are omitted in other drawings.

The male die 62 and the female die 44 define between them a cavity toreceive a moulded article 100 connected by a narrow neck 101 to adeadhead 102 that is accommodated partly in a conical bore 104 (FIG.-1)in the female die 44, partly in a transverse cavity 106 in the same die44 surrounding the tip of the nozzle 12, and partly within the cavity108 of the nozzle 12. 1

OPERATION OF THE PRESS After injection and cooling have taken place inthe usual manner, the press is opened. This is done by applying tractionto the plate 84 (FIG..1) by customary means, not illustrated. Thetraction is transmitted through the body 80 to the plates 60,61 and thehook 68 and through the hook 68 to the plate 42. The

cylinder 89, shaft 91 and plate move with the plate 84 until an advancedstage in the opening cycle, as will be seen later. The spikes 36 and 56are initially located at the ends of the slots 38 and 58 nearest thefixed plate 16.

The main phases in the opening cycle are seen in FIGS. 3 to 7. In FIG.3, traction on the plate 84 has been transmitted to the plates 61,60 and42, as mentioned above, drawing them outwardly by a distance L from theplate 32, which remains stationary since there is no tractive forceacting on it. The narrowneck 101 of the deadhead' 102 breaks, and thefemale die 44 separates from the deadhead, which remains in the nozzlel2 and is thus fixed relatively to the plate 32.

The full extent of the gap L is reached when the pin 56 abuts againstthe rebate 54 (FIG. 8) in the plate 50. At this stage the spikes 36 and56 and the pin 30 have not moved in the bolt 18.

Further traction on the plate 84 brings about the situation seen in FIG.4. Engagement of the spike 56 on the rebate 54 causes the spike S6 tobemoved forward by a distance L equal to the length of the slots 58 and38. The pin 30 and spike 36 naturally move with the spike 56, and theplate 32 is correspondingly advanced by the distance L. The deadhead 102is forced forward, free of the undercut nozzle tip 14, and falls clearof the plates of the press.

At this stage the head 24 of the bolt 18 engages the rebate 64 on theplate 42, preventing further outward movement of the plate 42.Simultaneously, the latch 74 of the book 68 rides up the cam surface 28of the bolt 18 against the resistance of the springs 76. This releasesthe latch 74 from the teeth 52 and allows the plate 42 to separate fromthe plates 60 and 61 to reach the position seen in FIG. 5. The hook 68naturally returns to its normal position under the action of the springs76 when the latch 74 has cleared the end of the bolt 18 The plates 32and 42 remain in the position seen in 1 FIG. 4.

In FIG. 5, the die cavity is open. The article ad from the plate 42,this distance being greater than the longitudinal length of the article100.

Ejection of the article 100 now takes place, as seen in FIG. 6, byadvancing the piston 91 of the cylinder 89, so causing the plate 90 tomove away from the plate 84 until it abuts against the plate 61. Theejector pins 92 force the article 100 out of the male die 62 and itfalls clear of the plates of the press.

With the press fully open, as seen in FIG. 6, operations such asbrushing of the plates may occur. Then the press is closed.

Closure begins by pushing the plate 84 inward, towards the plate 41.During the course of this movement the bolt 46 abuts against the plate42 and causes the plate 90 to move back relatively to the plates 60,61and 84 to its original position. As the plate 60 approaches the' plate42, the sloping face 78 of the hook 68 rides up the teeth 52 on theplate 42, so causing the latch 74 to engage the teeth 52 once again.

The gap L" has then been closed and the position of FIG. 4 is restored,except of course that the die cavity is empty.

Further inward movement of the plates 84,61,60 and 42 closes the gap Land brings the press to the position seen in FIG. 7. As seen in thatFigure, the spikes 36 and 56 and the pin 30 are still is their outermostposition from the fixed plate 16.

Finally, inward pushing of the plates closes the gap L to to return thepress to the position of FIG. 1. This movement also returns the pin 30to its original position, and the press is then ready for the next cycleof injection.

It should be noticed in FIG. 8 that the gaps between the plates 16,32,42and 60,61 have no significance, being chosen only for the sake ofillustration.

SInce the pins 30 are located within the bolts 18, less space isoccupied around the periphery of the dies 44,62 by the bolts 18 and pins30 than would be occupied in conventional presses by bolts separate fromthe bolts l8 and performing the same function as the pins 30.

I claim:

1. A moulding press having a plurality of plates and means to guide theplates for movement relatively to each other, such guide means includinga guide bolt extending between at least two plates, with the improvementthat the bolt is hollow and contains a sliding pin,

the pin having at least two transverse elements protruding through slotsin the bolt, each element being engageable with a plate to limit themovement of that plate relatively to another plate.

2. The press of claim 1 having a first plate to which one end of thebolt is connected, the bolt having a head on its free end, and a secondplate and a third plate that are slidable on the bolt, the third platebeing adapted to engage the head of the bolt to define the maximum gapbetween the first plate and the third plate, and in which the pin has afirst protruding element that is fixed to the second plate and a secondsuch element that is unconnected to any plate but is adapted to engage aseat in the third plate during opening of the press, thereby to causethe pin and the second plate to be moved together with the third plateaway from the first plate.

3. The press of claim 2, in which the first plate is a fixed plate ofthe press.

4. The press of claim 2, in which the third plate carries one member ofa die of the press, and including a fourth plate carrying a second diemember, the bolt having a cam at a point on its length and the fourthplate carrying a hook that engages a tooth on the third plate, the cambeing located in the path of movement of the hook and being adapted,when the hook engages the cam, to disengage the hook from the tooth, so

1. A moulding press having a plurality of plates and means to guide theplates for movement relatively to each other, such guide means includinga guide bolt extending between at least two plates, with the improvementthat the bolt is hollow and contains a sliding pin, the pin having atleast two transverse elements protruding through slots in the bolt, eachelement being engageable with a plate to limit the movement of thatplate relatively to another plate.
 2. The press of claim 1 having afirst plate tO which one end of the bolt is connected, the bolt having ahead on its free end, and a second plate and a third plate that areslidable on the bolt, the third plate being adapted to engage the headof the bolt to define the maximum gap between the first plate and thethird plate, and in which the pin has a first protruding element that isfixed to the second plate and a second such element that is unconnectedto any plate but is adapted to engage a seat in the third plate duringopening of the press, thereby to cause the pin and the second plate tobe moved together with the third plate away from the first plate.
 3. Thepress of claim 2, in which the first plate is a fixed plate of thepress.
 4. The press of claim 2, in which the third plate carries onemember of a die of the press, and including a fourth plate carrying asecond die member, the bolt having a cam at a point on its length andthe fourth plate carrying a hook that engages a tooth on the thirdplate, the cam being located in the path of movement of the hook andbeing adapted, when the hook engages the cam, to disengage the hook fromthe tooth, so separating the third plate and fourth plate.